Polyphase distributing system



C. LE G. FO RTESCUE.

P0l. YPHA SE DISTRIBUTING SYSTEM. AIPLICATION FILED SEPT- 30, I916.

1,376,419. I Patented May 3, 1921.

4 SHEETS-SHEET I.

WITNESSES V INV ENTOR Char/es LeC-l. F'o Tescue.

' ATTORNEY c. LE 6. FORTESCUE.

POLYPHASE DISTRIBUTING SYSTEM.

APPLICATION EILEI) SEPT. 30, I9I6.

1,376,419; May3,1921.

4 SHEETS-SHEET 2.

Fig. 2

WITNESSES: INVENTOR Char-[es Le Gk. F'orfescue.

' I BY ATTORNEY C. LE 6. FORTESCUE.

POLYPHASE DISTRIBUTING SYSTEM. APPLICATION FILED sEPT.30. 1916.

1,376,419. 7 Patented May 3,1921.

4 SHEETS-SHEET 3- INVENTOR Char/es L9G. Forfescue.

; ATTORNEY CL LE G. FORTESCUE.

POLYPHASE DISTRIBUTING SYSTEM.

APPLICATION FILED SEPT. 30, I9I6.

1,376,419. Patented May 3,1921;

SHEETS-SHEET 4.

. I INVENTOR Char/es Le 6.; Forfescue.

2 BY a 2 ATTORNEY UNITED STATES PATENT OFFICE.

CHARLES LE G. FORTESCUE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WEST INGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

POLYPHASE DISTRIBUTING SYSTEM.

Patented May 3, 1921.

Application filed September 30, 1916. Serial No. 123,031.

To all whom it may] concern.

Be it known that I, CHARLES LE G FoR- TmscUn, a subject of the King of England, and a'resident of Pittsbur h, in the county of Allegheny and State of ennsylvania, have invented a new and useful Improvement in Polyphase Distributing Systems, of which the following specification is a continuation -one number of phases into balanced polyphase currents of another number of phases.

It is desirable to select the loads on the several phases of a polyphase-distributing system so as to prevent excessive unbalanc iug of the phase-voltages and currents. Unless such care is exercised, the transmission system will not operate economically and its ultimate load capacity will be considerably reduced. Moreover. polyphase apparatus designed for balanced voltages and currents will be adversely affected when connected to an unbalanced polyphase system. For instance, undesirable temperatures may develop in portions of the polyphase apparatus unless such apparatus'is specially designed to carry unbalanced currents. Again, emergency conditions frequently demand that two or more polyphase systems be interconnected to effect an interchange of electrical energy between them.v But it is objectionable and inefiicient to do this when one of the sys tems is considerably.unbalanced because the unbalanced system will reflect its unbalanced conditions to any satisfactorily balanced system which may be connected to it.

It is well known that an ideal phase-balancer will also serve as a phase-splitter or converter to transform a single-phase current into balanced polyphase currents, and vice versa. Of course. when performing this function, the plmse-balancer is operating under such special conditions as may be represented by a phase-balancer that is connected to a polyphase system in which all of the loads are connected to a single phase thereof. or by a phase-balancer employed to maintain balanced polyphase conditions at a point in a normally balanced polyphase system that is connected to a single-phase system from which part of the power is supplied. lVhile one phase is loaded to the exclusion of the other phases, all of the phases contribute equal amounts of powerto the loaded phase throughthe intermediary of the phase-balancing means and vice versa. Since the phase balancer thus automatically eflects an equal division of power among the several phases of a polyphase system, it may also be considered as a phase-splitter or a phase-converter.

One object of my invention is to provide a phase-balancing means of the character above mentionedwhich will also serve, when special conditions require, as a phase-converter. The phase-balancing means of the present invention will also automatically effect an equal division of the load among the several phases of the source of supply, irrespective of the loading of the several phases of the load circuit, the power-factors of the load and other asymmetrical conditions obtaining therein.

For a better understanding of the nature and scope of my invention, reference may be had to the following description and the accompanying drawings in which Figure 1 is a diagrammatic view of a polyphase distributing system embodying a form of my invention, the phase balancing means, in this instance, comprising synchronous dynamoelectric machines; Fig. 2 is a dia ram of a modification of the system shown in Fig. 1; Fig. 3 is a view of a. system showing, diagrammatically, a modified form of the control system embodied in Fig. 1, and Fig. 4 is a diagrammatic view of a polyphase distributing system in which the phase-balancing means comprises dynamo-electric manent, has a phase rotation opposite to that of the said resultant system.

In an unbalanced polyphase power system, the unbalancing-component of the electromotive forces which, as stated above, constitutes a balanced polyphase system of vectors of opposite phase rotation to that of the system, will be proportional to the product of the unbalancing-component of the polyphase currents and the impedance of the system offered to the flow of said unbalancingcomponent of the wurrents. The relative division of the unbalancing-component of the currents among the various polyphase machines connected to the polyphase system will depend upon the respective impedances of said machines offered to the flow of the currents constituting the unbalancingcomponent. Synchronous machines and in duction motors oifer a very low impedance to the fiow of these counter-rotating or unbalancing-component currents, and, thence,

chines would serve as ideal phase-balancers' since, as will be hereinafter explained, the unbalancing-component of the load would be completely eliminated.

' When an unbalanced load is supplied from a polyphasesystem, all the polyphase rotating machines connected to the system v tend to act as balancers in order to keep the phase-voltages and phase-currents in balanced relations so that balanced polyphase conditions may be approached at the main bus-bars. In particular, symmetrical poly-., phase machines of low impedance, such as synchronous motors, rotary converters and induction motors, tend to maintain balanced conditions on the polyphase system independently of the load imposed on them.

To understand the theory of operation of the phase-balancer of the present invention, assume that a single-phase generator is a polyphase generator subjected to certain unbalanced load conditions. The polyphase generator supplyin the unbalanced load, in this instance, may e considered as being a three-phase generator having zero current flowing in one of its windings'and currents equal to the single-phase load-current flowing in the other two windings, the line current obtaining in one of its leads flowing in a direction opposite to that obtaining in the other lead. The generator comprises a rotating armature winding connected to the unbalanced polyphase system and a stationary field element on which a polyphase amoritisseur or auxiliary winding is disose p Since, as mentioned above, an unbalanced polyphase load may be resolved into two phase rotation are stationary with respectv I to the said amortis'seunwinding, while the counter phase rotating magneto motive forces, which havetlre same direction of rotation as that of the armature winding rela-I tive to the amortisseur winding, generate double-synchronous-frequency currents in the amortisseur win ding; The double frequency currents thus induced generate polyphase magneto-motive forces which approximate, in value, the magneto-motive forces generated by the unbalancing-component currents flowing in the armature winding. However, the magneto-motive forces generated by these induced currents in the amortisseur winding are not exactly equal to the magneto-motive forces inducing them, because the magnetic coupling or mutual induction between the main winding and the amortisseur winding is not entirely perfect. If it were possible to make this magnetic coupling completely perfect, and if the re-' sistance of the amortisseur and armature windings were zero to the-flow of the unbalancing-component currents, no reactions to these counter-phase rotating currents would exist and, therefore, the electromotive forces Y of the generator would be balanced.

It is desirable to exclude double-frequency currents from being induced in the directcurrent field winding of the machine because, if these currents obtain therein, they will react on the main winding of the machine in an undesirable manner.

From the foregoing analysis of a singlephase generator, it is evident that a singlephase impedance comprises two elements, namely, the effective impedance of the generator, considered as a polyphase machine, to the normal phase rotating or load-component and the effective impedance to the counter phase rotating or unbalancing component of the load. The former is the impedance of t e machine offered. t the flow of symmetrical polyphase currents of positive phase rotation and the latter is the impedance of the machine offered to the flow of symmetrical polyphase currents of countter-phase rotation.

The impedance of a dynamo-electric machine to the counter-phase rotational currents may be made extremely low by carefully designing the or damper winding. If, in addition, auxiliary means be provided, externally or internal ly of the machine, to assist the natural action ofthe machine as a phase-balancer, the admittance of the machine to the counter-phase rotational or unbalancingcomponent currents may be made infinite so that theterminal voltages of theimachine will be absolutely balanced irrespective of the amounts of counter-phase rotational currents the machine may be called upon to supply. Since the abilityof an unassisted dynamo electric machine to act as a balancer is measured by its impedance to the counterphase rotational'component of the unbalanced load, the action of such a machine when thrown upon an unbalanced polyphase system consists in supplying such amount of these counter-phase rotational currents or the unbalancing-component of the load as will bring the system and the machine to the same degree of unbalancing. The voltage balance of the system is thereby improved at the expense of the voltage balance of the machine. The voltages that cause an unbalance at the machine terminals are the impedance-drops resulting from thecounterphase rotational currents supplied by the machine and are, therefore, counter-phase rotational symmetrical polyphase voltages. Therefore, if means are provided for reducing to zero the effective impedance offered to the flow of the unbalancing-component of the currents in the polyphase system, the phases of said system would be maintained in strict polyphase relationship.

One well known method for assisting a polyphase machine to maintain a balance is to supply counter-phase rotational electromotive forces of the .proper magnitude and phase to said machine from an external source of power. The armature winding of said machine is electrically connected to the polyphase; mains, and counter-phase rotatlng polyphase electromotive forces, having the same frequency as those of the main dynamo electric machine, are impressed upon said armature winding from an auxiliary source of power that has its polyphase winding connected in series with said armature winding. These counter-phase rotating electromotive forces compensate for the impedance-drop and compel the said machine to offer zero impedance to the flow of the unbalancing-component of the load, thereby permitting current to be drawn from one polyphase amortissuer phase of the polyphase system through the main dynamo-electric machine and delivered to another or other phases of the system. The auxiliary source of power must be capable of having its electromotive forces, which comprise the counter-phase rotating electromotive forces introduced into the armature of the main machine, adjustable in phase and in magnitude with the varying degrees of unbalancing obtaining in the power system.

By means of my present invention, balanced polyphase conditions may be maintained in a polyphase distributing system by neutralizing the magneto-motive forces generated by the unbalancing-component of the load. As a result, the reactions occasioned by the said unbalancing-component of the .load will'be reduced to zero. In order to neutralize the magneto-motive forces resulting from this unbalancing-component of the load and thereby maintain balanced polyphase conditions only in the supply system, I provide a phase balancer that comprises a main dynamo-electric machine in which polyphase currents of the proper frequency, magnitude and phase displacement are introduced so that the afore mentioned magneto-motivetforces of the unbalancing component of-the load may be neutralized, irrespective of the load conditions obtaining in the power system. As a result, the terminal voltages of the main machine of the phase balancer will be automatically maintained in a perfectly balanced relation, irrespective of the distribution of the loads in the several phases of the distributing system.

Other features of novelty of my invention will be pointed out with particularity in the claims annexed to form a part of this specification.

Referring to Fig. 1, a source of alternating current supply 1 is connected to polyphase mains 2, 3 and 4 of an electric power-distributing system. Unbalanced load conditions may be imposed on this distributing system, for example, by connecting translating devices to a single-phase feeder 5 that is connected across the phase 23 of the distributing system. The loads obtaining in the feeder circuit 5 tend to lower the voltage between the mains 2 and 3. At the same time that the unbalanced voltage conditions obtain, unbalanced current conditions in the'several phases of the distributing system will exist.

In order to correct this unbalancing of the voltage between the distributing mains, I provide a phase-balancer 6 which, in this instance, comprises a main synchronous dynamo-electric machine 7 and an auxiliary synchronous dynamo-electric machine 8. The

rotor 9 of the main machine 7 is represented as comprising a Y-connected winding having its free terminals connected to slip rings 10 that, in turn, are connected to the mains 2, 3 and l by leads 11. The field element of the synchronous machine 7 comprises a single pair of poles that are provided wltli field coils 12 and 13. The field winding 1S excited by means of an exciter 14 having a field winding 15 and a resistor 16 connected in series therewith, the effective value of which is controlled by means of a vibrating contact regulator 17 of the Tirrill type.

The vibrating electromagnet of the regulatorl? is excited. through mains 18 which, in turn. are connected across the phase 2-4: of the distributing system. A parallel resonant shunt 19 is connected in series with the field winding of the synchronous machine 7 in order to preclude currents of a certain frequency, in this instance, double-frequency currents, from flowing therethrough, as will be hereinafter described.

The stator of the machine 7 is also provided with an auxiliary winding 20 which I designate as a polyphase amortisseur winding. It is apparent that the rotor winding 9 of the main machine? is subjected to the excitations arising from both the direct-current salient-pole field winding and the polyphase winding 20.

The auxiliary dynamo-electric machine 8 comprises a polyphase rotatable winding 21 that has its terminals connected to slip rings 22.- The stator of the auxiliary machine 8' comprises eight salient-pole members formed into two groups each of which consists of two north poles and two south poles. The two groups of poles are so wound that adjacent pole members of the two difl'erent groups have the same polarity. That is, a north pole of one group is adjacent to the north pole of the other group and the south pole of one group is adjacent to the south pole of the other group. One group of the poles is excited by a field winding 23 which is supplied with current from an exciter 24. The other group is wound with a field winding 25 that is excited by means of an exciter 26.

The exciters 2d and 26 are provided with field windings 27 and 28, respectively, the excitations of which are controlled by means of two Tirrill regulators 29 and 30 that serve to regulate the effective value of resistors 31 and 32, connected in circuit with the field windings 27 and 28, respectively, The vibrating electromagnet of the regulator 29 is excited through leads 33 that are connected across the phase 34 of the distributing system, and the vibrating electromagnet of the regulator 30 is excited through one of the leads 33 and a lead 34 that are connected across the phase 2-3 of the distributing system. The rotatable winding 21 of the auxiliary machine 8 is connected, by means of leads 35, to suit ble points upon the poly as the phase either be and t e supply generator 1. At the sametime, I desire to be able to shift thephase of the voltages induced in the rotor wmdmg 21 of the auxiliary machine 8 as well as to vary the magnitude of these induced voltages. To this end, the auxiliary machine'8 is provided with eight poles which, in the aggregate, are the equivalent of four poles since adjacent ones are of the same polarity, as mentioned above. By separately varying the excitation of the field windings 23 and 25, the magnitude, as well position, of the voltages induced in the winding 21 may be controlled with respect to the voltages of the main machine 7.

This is automatically eflected by means of the two Tirrill regulators 29. and 30 which are influenced by the conditions obtaining in the distributing system. The

two field windings 23 and 25 of'the auxiliary machine 8 have their magnetic axes arranged at substantially ninety electrical degrees from one another and, therefore, by separately varying the excitation of the two windings, both the magnitude and phase relationship of the resultant field influencing the rotor winding 21 may be controlled. The auxiliary machine 8 ma connected to the shaft of the main machine 7 or be rotated at synchronous speed byan auxiliary device. It is probably preferable to mechanically connect the machine 8 to the machine 7 to rotate the armature winding 21 of the auxiliary machine.

To understand the operation of my phasebalancing means, consider that the unbalanced load conditions obtaining in the distributing system cause unbalanced voltages to be impressed uponthe terminals of the rotor winding 9 of the main machine 7. The resulting unbalanced polyphase currents flowing in the several phases of the winding 9 generate a resultant field which is established by two component, synchronously-rotating systems of balanced polyphase magneto-motive-forces, one component system of magneto-motive-forces having the same phase rotation as the direction of rotation of other component system of magneto-motiveforces having a phase rotation the direction of which is opposite to that of the roto windin 9.

The balanced component system of mag neto-motive-forces having a phase rotation that is opposite the direction of rotation of the rotor winding 9 is the one that'I have 1 previously designated as being the load-comonent. The balanced component system tion rotation of the rotor winding 9 is the i one that I have previously designated as being the unbalancing-component. fore, the load-component system of magneto-motive forces is stationary with res ect to the stator and the auxiliary polyp ase windings, while the unbalancing-c'omponent system of magneto-motive forces induces p'olyphase, double-frequenc currents in the Y pogphase amortisseur win ingo20.

ouble-frequency currents are precluded from flowing in coils 12 and 13 of the field winding because the parallel resonant shunt 19 is inserted in series therewith and tuned to doublesynchronous frequency. The shunt 19 is not essential but confines the flow of the double-frequenc currents to the winding 20. If doublerequency currents were permitted to flow in the field coils 12 and 13, undesirable harmonic voltages would be induced in the main winding 9. As mentioned above, if, under all conditions, the effective impedance offered to the flow of the unbalancing-component currents flowin in the winding 9 were reduced to zero, t is voltages across the terminals of the main machine 7 would be maintained in bal-.

anced polyphase relationship with one another, which conditions would be reflected upon the distributing system, thereby maintaining balanced polyphase conditions therein. The effective impedance offered by the winding 9 to the flow of the unbalancingcomponent currents is reduced to zero by subjecting the system of balanced polyphase magneto-motive-forces generated by these nnbalancing currents to another system of magneto-motive forces having the proper phase displacement and magnitude.

The unbalancing-component system of magneto-motive-forces induces double-frequencypolyphase currents in the amortisseur winding '20 and the magneto-motive forces arising therefrom tend to react upon the said inducing magneto-motive-forces to reduce them to zero, in accordance with a well-known principle. perfect magnetic coupling between the inducing winding 9 and the induced winding 20, by reason of the magnetic leaka the resistance and .reactance of sai windings, the double-frequency.currents induced in the winding 20 are not of sufficient magnitude to completely neutralize the unbalancing-component system of magneto-motive forces. To this'end, doublefrequeney curavin r the same phase rotation as the direc- Thereload conditions.

Because of the ime, and

rents of the proper value. and pha'se-disv placement namely those enerated in the rotor'win mg 21 o the-auxiliary machine 8,

are introduced into the winding 20 in order to augment the double frequency currents nduced therein. If the currents introduced nto the amortisseur winding 20 by the windmg 21 are of the proper. ma njtude and phase displacement, the unba ancing-com- Eonent s stem of ma neto-motive forces will e comp etel neutra ized and the impedance. offered by t e winding 9 to the flow of the unbalancmg-component currents will be reduced to zero. The unbalancing component of the load is thus offered a zero impedance 1n the wmding 9 of the machine 7, and therefore, the terminal voltagesof said machine are maintained perfectly balanced underall These balanced conditions are reflected into the distributing system that, in turn, operates under balanced polyphase conditions, irrespective, of the loading of its several phases.

The regulators 17,29 and 30 are similar in construction and, consequently, the operation of one of them only will be explained.

For example, the regulator 30 comprises an electromagnet 36 WhlCh controls a vibratory armature 37 working against a spring 38.

.The vibrating armature 37 controls the effective resistance of the resistor 32 which is connected in circuit with-the field winding 28 of the exciter 26. The regulators 29 and 30 are arranged so that, when the voltage between two of the mains of the distributing system is high, one of the resistors 31 or 32 will be short-circuited and the excitation of the field-magnet winding of the associated wise increased which effects an increase in the corresponding field component of the auxiliary machine 8.

When the voltage between mains 2 and '3 exceeds normal value, the corresponding regulator 30 operates to increase the voltage of the exciter 26 which, in turn, increases the excitation of the field winding25 of the auxiliary machine 8. The increase in value of the magneto-motive force generated by the field winding resultant field o the auxiliary machine 8 and changes the phase displacement of the voltages induced in the windin 21 59 as to effect a complete neutralizatlon of the s a 25 effects a shift in the system of unbalancing-magneto-motive forces obtaining 1n the main machine 7.

When the unbalancingwomponent magnetomotive forces are completely neutralized, as mentioned above, the winding 9 offers zero effective impedance to the unbalancingcomponent of the, unbalanced currents and balanced polyphase conditions will be restored upon the mains 2, 3 and 4. In this manner, the magnitude and phase position desired, the field windings 12 and 13 may be over-excited in order to compensate for the lagging power-factor 'under which the loads, fed by the distributing System, usually operate. By proper adjustment ofthe field excitation of the machine 7, the power-factor of the distributing system ma be controlled and raised to substantia ly unity while, at the same time, the machine 7 also serves as a portion of the phase-balancing means for'the distributing system.

The system shown in Fig. 2.is somewhat similar to that of Fi 1 with the exceptlon of the main machine ,-which is replaced bx a main dynamo elcctric machine 40. stator winding 41 of thema'chine 40, which I designate, for convenience, as the prlmary winding, is connected to the 1113.11182, 3 and 4. The rotor winding 42 is a distributed winding serving as a non-salient two-pole winding for the direct-current field excita'' tion of the synchronous machine 49 and also as a polyphase amortisseur windlng. The winding 42, therefore, replaces w1nd1ngs'12,

13 and 20 of the main machine 7 of Fig. 1. i

The rotor winding '21 of the auxiliary machine 8 is connected, through the slip rings 22 and the leads-35, to suitable points or taps upon the winding 42 that extend to the slip rings 43. :Slip rings 44, connected to diametrical taps on the winding 42, serve to conduct directcu'rrent flowing from the exciter 14in order to furnish excitation 1 0.

the non-salient poles ofthe main machine.

While the auxiliary machine 8' is represented as being a synchronous machine and, therefore, capable of being driven by an auxiliary source of power, I have shown the rotor thereof as being mechanically connected to a shaft 45 of the main machine 40.

Since the main machine 40 is of the synchronous type, the actions obtaining therein by reason ofthe unbalancing of the supply mains 2, 3 and 4 are similar to those obtaining in the main machine 7 of Fig 1. For

instance, when unbalanced polyphase currents traverse the stator winding 41, two synchronously rotating balanced polyphase systems of magneto-motive forces are generated, one component s stem having a phase rotatiomin the direction of rotation of the rotor winding 42 and the other compo-1 nent system having a counter phase rotation. The component system rotating with the rotor windlng 42, is the load-component and, therefore, induces no alternating currents in the rotor winding 42. The unbalancing-component rotates atsynchronous speed with respect to the stator in a direc- :e'xplained in connection with tion opposite tothe rotation of the rotor and thereby induces in the rotor winding 42 alternating .currents having twice the frequency of the currents obtaining in the sup: ply mains 2, 3 and 4. In this case, the unf'balancing-component system of magneto-- ,motive forces must be neutralized, asexlisli and maintain balanced polyphase conditions in the distributing. mains 2, 3 and 4. .The auxiliary machine 8, therefore, furnishes double frequency currents of the proper magnitude and phase relationship to the'rotor winding 42 in order to completely neutralize the aforementioned. unbalancingcomponent magneto-motive forces.

. The direct-current field excitation of the main machine 40 is controlled by the Tirrill regulator 17 and,"similarly, the magnitude and phase of the voltages induced in the rotor winding 21 of the machine 8 are plainedf in connection with the main macontrolled by the'T-irrilLregulators 29 .and

30. These regulators operate in \the manner the regulator :30 of Fig. 1.

' means similar to the systems shown in Figs. 1 and 2 that is adapted to maintain balanced polyphase conditions in a two-phase disa two-phase amortis'seur winding 55 in which alternating currents are introduced.

I The two field windings 53 and 54 are excited by means of the exciter 14 which is similar in all respects tothe exciter of Figs. 1 and 2. The auxiliary machine 56 comprisesa stator that is rotated by means" of a wormand-wheel mechanism 57 that, in turn, is

operated by means' o'f an induction motor 58. The stator of the auxiliary machine 561 In Fig. 3, I haveshown a phase-balancing is wound with a two-phase winding 59 one phase thereof being excited by an adjustable transformer 60 and the other phase being excited by an adjustable transformer 61.. The rotor of the auxiliary machine 56 comprises a two-phase winding 62 that; is connected, through slip rings 63 and leads 64,

to the proper terminals of the polyphase amortisseur winding 55 of the main inachine 50.

impedance by the main machine 50, as ex- In this system, the unbalancing-compd' nent currents are to be offered zero efi'ective troducing double-frequency currents of the proper phase displacement and magnitude in the polyphasc amortisseur winding of the main machine 50. The double-frequency currents thus introduced are generated in the rotor winding (32 of the auxiliary machine 56 which is so designed as to have the same number of poles as the main machine 50. Since the stator winding 59 is ex cited by currents of synchronous frequency and the rotor winding 62 is, rotated at synchronous speed and in the direction opposite to the rotation of the field established by the stator currents, the currents induced in the rotor winding (52'liave double the frequency of the currents obtaining in the power mains. The rotor of the auxiliary machine 56 may be mounted either upon a common shaft with the. rotor of the main machine 50 or driven at synchronous speed by means of an auxiliary source of power (not shown).

The magnitude and phase of the doublet'requency currents generated in the winding (32 of the auxiliary machine 56 are controlled by the transformers 60 and 61 and the induction motor 58, respectively. The secondary windings of the transformers 60 and ()1 are severally provided with a plurality of taps ()5 that are engaged by means of movable contacts ,66 mounted upon an oscillatory shaft 67. The ends of the shaft (57 are provided with magnetic cores 68 that are influenced by energizing coil windings 69. The two energizing windings 69 are severally connected to thetwo phases of the distributing system. WVhen the voltage of one of the phases exceeds that of the other phase, the predominating actuating winding 69 will simultaneously move both of the contact members 66 to engage the proper taps upon the secondary windings of the two transformers. In consequence thereof, the excitation of the stator winding 59 is varied which, in turn, varies the magnitude of the voltages induced in the rotor winding 62.

Phase adjustment of the voltages induced in the winding 62 is controlled by rotating the stator winding 59 by the worm-andwheel mechanism 57. A

The direction of rotation of the stator winding. as well as the degree, is controlled by means of a relay 70. The relay 70 comprises a rocking lever 71 to both ends of which are pivoted magnetizable plungers 72. The plungers 72 are influenced by magnetizing windings 73 that are severally connected to the two phases of the distributing circuit. A contact-making arm 74 is rigidly secured to the lever 71 and is provided with two insulated conducting portions 75 that are adapted to engage stationary contact members 76 and 77, depending upon which magnetizing winding 73 predominates in theattraction for the plungers 72. The diof synchronous machines, but it is apparent rection of rotation of the induction motor, 58 is controlled by means of the relay 70, which, when unbalanced conditions obtain in the distributing system, establishes circuits either through the contact members 76 or the contact members 77.

By properly positioning the stator winding 59, currents of the proper phase relationship are induced in the rotor winding 62 ot' the auxiliary machine 56. Since the currents generated in the winding 62 are automatically controlled, both in magnitude and. phase relationship, in accordance with the unbalanciug conditions obtaining in the several phases of the distributing system, complete neutralization of the unbalancing component field in the main machine 50 is se-.

cured and the impedance offered by the winding 51. ot' the machine 50 to the counterphase rotational or unbalancing currents is reduced to zero.

The hereinbefore described systems embodying my phase-balancing means have been confined exclusively to the employing that machines of the induction type may be used. Under this circumstance, the rotors of the induction machines may rotate at synchronous speed when the losses of the induction machines are supplied from an auxiliary source. In this case, the induction machines act as synchronous machines, wherefore, the electrical conditions obtain ing therein correspond to those obtaining in the synchronous machines of the systems shown in Figs. 1, 2 and 3. When the induction machines are not supplied with power from auxiliary sources to compensate for their internal losses, account must be taken of the slip between the synchronously rotating fields generated by the polyphase currents flowing in their primary windings and the speed of the rotors of the machines.

In Fig. 1, a phase balancing system comprising a machine of the induction type is shown. An induction machine 80 has its stator winding 81 connected to mains 82, 83 and 8 1 of a three-phase distributing system upon which it is desired tomaintain balanced polyphase conditions irrespective of the single-phase loads connected to a feeder circuit 85.. The rotor of the induction machine 80 is provided with a secondary winding 86 which is short circuited through a resistor 87. The winding 86 is also connected, at a plurality of spaced points,'to a commutatingcylinder 88. Brushes 89, equal in number to the phases of the distributing system, are mounted in equally spaced relation upon the end of a shaft 90 and are arranged to bear upon the commutating cylinder 88. The shaft 90 is driven, at synchronous speed, by a suitable synchronous motor 91 that is connected to leads 92 which, in turn, are connected to the three-phase distributing mains machine 80. One system of these magneto-.

of the distributing system. Three equally spaced points in the armature WlIlCllIlg 94: of

' the generator 93 are connected, by means of suitable leads 95, to the brushes 89. Two of the leads 95 are crossed, as indicated, so that the rotating field produced by the alternating currents supplied to the winding 86 through the brushes 89 and the commutator cylinder 88 rotates in a negative..d1rection with respect to the direction of rotation of the main machine 80 and the auxlllary motor 91.

As explained above, the unbalanced polyphase conditions obtaining in the supply mains 82, 83 and 84; result in the production of two systems of synchronous, balanced polyphase magneto-motive forces in the mam motive forces, designated as the load-component, which is usually the larger of the two, has the same phase rotatlon asthe rotor winding 86. Therefore, the relative speed between the load-component magneto-motive forces and the rotor corresponds to slip frequency. The unbalanci-ng-component magneto-motive forces which are usually the smaller of the two, have a counter-phase rotation relative to the stator and in' a direction opposite to the rotation of the rotor. Therefore, with respect to the rotor, the unbalancing-component magneto-motive forces rotate at double frequency minus slip frequency. hese unbalancing component magneto-motive forces induce currents in the winding 86 of twice-synchronous frequency minus the slip frequency.

If the rotor operated at synchronous speed as in a synchronous dynamo-electric machine or if the synchronous motor 91 supplied theinternal losses of the main machine 80, the currents induced in the rotor winding 86 by the unbalancing component magneto-motive forces would be of twice synchronous frequency. Assuming that the interal losses of the machine 80 are not supplied by the motor 91, allowance must be made for the slip obtaining between the rotor winding 86 and the synchronously rotating load component magneto-motive forces. The currents induced in the rotor winding 86 by reason of the unbalancing component magneto-motive forces tend to neutralize them but, because of the imperfect magnetic coupling between the rotor and the stator windings and for other reasons, this c annot be completely efi'ected. Therefore, currents of the proper value, phase displacement and frequency, are introduced into the rotor winding 86 in order to augment the currents induced therein by the unbalancing component magneto-motive forces so as to completely neutralize them and, therefore, reduce the effective impedance of the winding 81 to the flow ofthe unbalancing component currents. To this end, the synchronous generator 93 is provided.

The motor 91 rotates the brushes 89 at synchronous speed in the direction of rotation of the commutatin cylinder 88. The commutating cylinder, of course, rotates at a speed corresponding to synchronous frequency minus slip frequency. The relative speed between the brushes 89 and the commutating cylinder 88 is, therefore, slip frequency. The synchronous machine 93 supplies, through the leads 95, double-frequency magneto-motive forces having a ase rotation in a direction opposite to t e rotation of the rotor winding 86. Since these doublefrequency currents from the generator 93 are introduced into the rotor Winding 86 through the brushes 89, the resultant fre quency of these currents introduced in the rotor winding 86, is equal to twice synchronous frequencv minus slip frequency. These currents augment the currents induced in the rotor winding 86 by the unbalancing-component magneto-motive forces and, since they are of the proper magnitude and phase relationship, the unbalancingcomponent magneto-motive forces, established by reason of the unbalanced polyphase currents obtaining in the distributing system, are completely neutralized. From the foregoing, it will be apparent that, by injecting currents of the proper frequency into the rotor winding 86 of the induction machine 80, the balancing action of the machine may-be suitably. performed.

The short-circuiting resistor 87 is prefer abl Wound inductively so that the relatively hig -frequency currents supplied to the commutating cylinder 88 will have less tendency to flow through this winding than through the rotor winding 86, while thecurrents of slip frequency will not be impeded to any appreciable extent.

In order to control the magnitude and hase'of the augmenting current introduced into the rotor winding 86 of the main machine 80, the field windings of the auxiliary machine 93 are controlled by means of Tirrill regulators, as explained in connection with the system shown in Fig. 1.

It is obvious from the foregoingdescriptions of the several systems that my phasebalancin means may be employed as a phase-splitter to convert alternating currents of one number of phases into alternating currents of another number of phases. To illustrate, single-phase alternating current may be supplied to one phase of the stator winding 81 of Fig. 4 and balanced currents that generate rotating-polyphase three-phase currents will consequently be furnished to the three-phase mains 82, 83

r and 84. The systems shown in Figs. 1 2, and 3 are also adapted to operate as phasesplitters or converters.

While each of the foregoing systems shows anauxiliary polyphase dynamo-electric machine for introducing symmetrical polyphase alternating currents into the amor- 'tiss'eur winding of the main. machine comprising the phase balancer, a single-phase machine ma under certain conditions, be

' substituted or the polyphase auxiliary mawinding by reason of the unbalancing-comchine. It is Well known that any stationary eriodic function, such as a vector represent-' 1ng single-phase alternating electromotive force, may be resolved into two oppositely rotatlngperiodic functions of half the amplitude. With this method of analysis in mind, a singlehase alternating current introduced into t e amortisseur winding may be considered as generating two rotating magneto-motive forces, one of which amplie.

fies the magneto-motive forces arising from the currents induced in the amortisseur ponent currents flowing in the primary winding of the main machine. The rotating magneto-motive-force serving in this manner may be controlled, both in phase and magnitude, by the methods emplo ed in the systems hereinbefore described. he other rotating magneto-motive-force, arising from the single-phase alternating current, unless neutralized or suppressed, will cause distortions in the voltage waves of the main ma-- chine. For this reason, the use of a singlephase auxiliary machine is not preferred over that of a polyphase auxiliary machine.

Again, the polyphase auxiliary machine may not be such as to generate symmetrical polyphase currents but each phase winding of the machine may be separately, controlled in order to vary both the magnitude and the phase-displacement of the electromotive forces generated therein. This method of control is old in the art and is the equivalent of that obtained by utilizing a plurality of separate machines having displaced armature windings, each of which is separately controlled. The polyphase currents introduced into the amortisseur winding from an auxiliary source of this character may likewise be resolved into two balanced polyphase systems, as explained above, one system of balanced polyphase currents serving to amplify the currents'induced in the amortisseur winding in-order to maintain balanced symmetrical phase conditions in the main machine. The other system of polyphase currents, unless neutralized or suppressed, will distort the electromotive force waves of the main machine and, therefore, this system is not to vbe preferred because it would require complicated auxiliary .balancing conditions obtaining in said polyancmg action upon the main machine.

While I have shown my invention in a plurality of forms, it will be obvious to those skilled in the art that it is not limited to any of these specific forms but is susceptible of various changes and modifications that do not depart from the spirit and scope thereof. I desire, therefore, that only such limitations shall be placed upon my invention as are imposedfby the prior art or as fall within the scope of the appended claims.

I claim as my invention:

1. A dynamo-electric machine for use as a shunt phase balancer for a polyphase distribution system, including, in combination, a polyphase induced winding adapted for connection across said distribution system, aninducing winding, and means for supplying to said inducing winding currents of the proper frequency, magnitude and phase toaugment the induced currents obtaining in said machine by reason of the unphase supply system.

2. A phase balancer comprising a dynamo-electric machine having an induced winding adapted for connection to a polyphase distributing circuit an inducing polyphase winding in inductive relation thereto, and means for supplying alternating currents of the proper magnitude and phase to said inducing winding, said currents having the same frequency as the cur- 1 0 rents induced in said inducing winding by the unbalancing-com onent magneto-motive forces arising rom the unbalanced currents traversing said induced winding, to au ment them.

3. phase balancer comprising a synchronous dynamo-electric machine having 'one of its polyphase windings adapted for magnetic members, a main polyphase winding on one of said members adapted for connection to a polyphase distributing system, a polyphase. exciting winding on the other of said members, unidirectional exciting means for said exciting winding, and '125 means for superposing upon the normal excitation of said exciting winding doublesynchronous frequency magnetomotive forces of the proper phase and magnitude, in order to reduce the effective impedance 13o of said main winding to the unbalancingcomponent currents traversing said main winding. a

5. A phase balancer comprising a synchronous dynamo-electric machine, an auxiliary dynamo electric machine having double the frequency ofsaid first machine, the phase relation of said machines being such and the connections between them being such that the current generated in said auxiliary machine may inductively influence the terminal electromotive forces of said main machine to maintain symmetrical polyphase relations, and means for relatively changing the phase displacement between the voltages of said machines.

(5. A phase balancer comprising a poly-- phase synchronous dynamo-electric -machine having one of its windings adapted for connection to a polyphase distributing system, and means for superposing upon the normal excitation thereof magnetomotive forces of double synchronous frequencyand of the proper phase and magnitude in order to maintainbalanced polyphase conditions in said winding.

7. A phase balancer comprising a synchronous polyphase dynamo-electric machine having one of its windings adapted for connection to a polyphase distributing system, a second winding in inductive relation thereto, and means for introducing into said second winding polyphase currents of double-synchronous frequency and of the proper magnitude and'phase to augment the currents. induced in said second winding by reason of the unbalancing-component currents of the load currents obtaining in said first winding. 7

8. The combination with a polyphase supply system, of a polyphase synchronous dynamo-electric machine. connected thereto, and means for supplying to said synchronous machine currents of double-synchronous frequency and of the proper magnitude and phase to augment the induced currents obtaining in said machine by reason I of the unbalancing of said supply system.

9. A phase balancer comprising a synchronous dynamo-electric machine having one of its windings adapted for connection to a polyphase distributing system, a second polyphase winding in inductive relation thereto, and means for supplying doublesynchronous-frequency currents to a plurality of phases of said second winding to augment the currents induced therein by the unbalancing-component magneto-motive forces resulting from the unbalanced currents traversing the said first winding.

10. In a polyphase system of transmission, a phase balancer comprising a synchronous polyphase dynamo electric machine having primary and secondary windings, and an adjustable source of alterna ing electromotive forces of double-synchronous frequency connected to said secondary Winding and adapted to neutralize the unbalancing component magneto motive forces resulting from the flow ofunbalanced currents in said dynamo-electric machine.

11. In a polyphase system of transmission, a phase balancer comprising a polyphase dynamo-electric machine having one of its windings adapted for connection to said transmission system, and an auxiliary adjustable source of alternating electromotive forces of substantially double frequency connected thereto and operating to lnduce alternating voltages of the proper phase and magnitude in the circuits of said first winding for neutralizing the reactions set up by said machine to the unbalancing-component of the currents obtaining in said polyphase system.

12. In an electrical system of distribution, the combination of a polyphase supply line which is subject to unbalance, thereby forming, in effect, major and minor balanced p0 opposite phase-sequence, a main synchronous dynamo-electric machine having a pair of relatively rotating magnetic members, a polyphase primary winding disposed on one of said members and connected across said supply circuit, a polyphase secondary Windyphase components of line frequency and exciting means tending to produce a unidirectional flux in said second mentioned member, an auxiliarypolyphase dynamoelectric machine having a pair of relatively rotating magnetic elements, an inducing winding on one of said elements, an induced winding on the other of said elements, the speed of rotation of said elements relative to each other being such that currents of twice said line frequency are generated in said induced winding, the arrangement being such that the relative phase-angle between the fields set up in the inducing and induced windings may vary in accordance with conditions 1n the main machine, the induced winding of the auxiliary machine being connected to the secondary winding of the main machine, and means for varying the currents generated in the induced winding of the auxiliary machine, whereby the opposite'phase sequence, a main synchronous dynamo-electric machine having a'pair of relatively rotating magnetic members, a polyphase primary winding disposed on one of said members and connected across said supply circuit, a polyphase secondary winding disposed on the other of said members, an auxiliary polyphase dynamo-electric machine having a pair of relatively rotating magnetic elements, an inducing windin on one of said elements, an induced 'win ing.

on the'other of said elements, the speed of rotation of said elements relative to each I other being such that currents of twice said for variabl exciting the inducing winding of the auxi iary machine. I

15. A system as specified in claim 14, characterized by the fact the exciting means for said" auxiliary machine supplies unidirectional current.

16. A system as specifiedin claim 14, in combination with a source of electromotive force connected with the secondary winding of said main machine for predetermining the speed thereof.

17. A system'as specified in claim 16, in combination with means for impeding the flow of double-frequency currents in the circuit of said source.

18. In an electrical system of distribution, the combination of a polyphase supply line which is subject to unbalance, thereby formin in effect major and minor balanced po lyphase components of line frequency and opposite phase-sequence, a main synchronous dynamo-electric machine having a pair of relatively rotating magnetic members, a polyphase primary winding disposed on one of said members and connected across said supply circuit, a polyphase secondary winding disposed on the other of said members, an auxiliary polyphase dynamo-electric machine having a pair of relatively rotating magnetic elements, and inducing winding on one of said elements, an induced winding on the other of said elements, the speed of' rotation of said elements relative to each other being such that currents of twice said line frequency are generated in said induced winding, the arrangement being such that the relative phase-angle between the fields set up inthe inducing and induced windings may varyin accordance with conditions in the main machine, means connecting the induced winding of the auxiliary machine to the secondary winding of the main machine in such manner that said secondary winding has impressed thereon electromotive forces of the same frequencyasthe electromotive forces generated therein b reason of currents corresponding to sai' minor balanced polyphase component in said primary windmg, and excitingmeans for-exciting the in ducing windingof theauxiliarymachine in accordance with the magnitude of 'said' minor balanced polyphase component. 19. A system as specified in claim 18,

characterized by the fact that the exciting means for said auxiliary machine supplies unidirectional current. 20. A system as specified in claim 18, in combination with a source of electromotive force connected with the secondary winding of said main machine for predetermining the speed thereof.

21. A system as specified in claim 20, in combination with means for impeding the flow of double-frequency currents in the circuit of said source.

22. A phase balancer comprising a dynamo-electric machine. having a winding adapted for connection to a olyphase distributing circuit, a second po yphase winding in inductive relation thereto, said windings being rotatable relatively to each other and means for supplying polyphase sym-' metrical alternating currents of the proper magnitude and phase displacement to said second winding, said currents having the same frequency as the currents'induced in said second winding by the unbalancingcomponent magneto-motive forces arisingfrom the unbalancing currents traversing said winding, to augment them. 7

23. A phase balancer comprising a synchronous dynamo-electric machine having one of its polyphase windings adapted for connection to a polyphase distributing sys- 'tem, a second polyphase winding in inductive relation thereto, and means for introducing symmetrical polyphase double-frequency currents of the propermagnitude and phase displacement into said second winding in order to maintain balanced polyphase conditionsin said first winding.

24. A phase balancer comprising a synchronous dynamo-electric machine having two windings, and an auxiliary adjustable source of symmetrical polyphase alternating electromotlve forces of double-synchronous frequency connected to oneof said windings and adapted to reduce to zero the eflective impedance of another of said windings to the flow of the unbalancing-component of currents traversing said first machine,

whereby balanced polyphase conditions may be maintamed.

25. A phase balancer comprising a polyphase dynamo-electric machine having one 5 of its windings adapted for connection to distributing mains and a second winding in inductive relation thereto in which superfrequency alternating currents are induced by the unbalancingcomponent currents 10 flowing in said first windingy and means for amplifying the said alternating current inducedin the second winding in order that the unbalancing-component magneto-motive forces obtaining in said machine may be reduced to zero.

29th da of Se t. 1916. D p

CHARLES LE G. FORTESCUE. 

